Nitroglycerin is known as a medicine for angina pectoris (i.e., a coronary vasodilator) and is used in an ointment form which can be sealed and stored.
Recently, a pharmaceutical preparation in a tape form has been proposed, which comprises a backing and a pressure-sensitive adhesive layer with nitroglycerin incorporated thereinto on the backing. This type of pharmaceutical preparation, however, has not yet been put into practical use, since it cannot be stored due to the high volatility of the nitroglycerin, and the excessive percutaneous absorbability of nitroglycerin causes harmful side effects such as skin irritator.
Isosorbide dinitrate (ISDN) and pentaerythritol tetranitrate (PETN) are known to be effective in the suppression or prevention of attacks of angina pectoris, and they are generally used in a tablet form. From a viewpoint of suppression or prevention, it is desirable that they are supplied into the body at a constant rate, and gradually over a long period of time.
Various attempts, therefore, have been made to control the solubility characteristics of the tablet. However, since the absorbability of medicine varies depending on the pH in the stomach or intestines, the presence of contents, etc., it is generally impossible to supply the ISDN or PETN at a constant rate and gradually over a long period of time.